ceph/src/boost/libs/hana/include/boost/hana/transform.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::transform`.
   4
   5 @copyright Louis Dionne 2013-2016
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_TRANSFORM_HPP
  11 #define BOOST_HANA_TRANSFORM_HPP
  12
  13 #include <boost/hana/fwd/transform.hpp>
  14
  15 #include <boost/hana/bool.hpp>
  16 #include <boost/hana/concept/functor.hpp>
  17 #include <boost/hana/concept/sequence.hpp>
  18 #include <boost/hana/config.hpp>
  19 #include <boost/hana/core/dispatch.hpp>
  20 #include <boost/hana/core/make.hpp>
  21 #include <boost/hana/functional/always.hpp>
  22 #include <boost/hana/fwd/adjust_if.hpp>
  23 #include <boost/hana/unpack.hpp>
  24
  25
  26 BOOST_HANA_NAMESPACE_BEGIN
  27     //! @cond
  28     template <typename Xs, typename F>
  29     constexpr auto transform_t::operator()(Xs&& xs, F&& f) const {
  30         using S = typename hana::tag_of<Xs>::type;
  31         using Transform = BOOST_HANA_DISPATCH_IF(transform_impl<S>,
  32             hana::Functor<S>::value
  33         );
  34
  35     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  36         static_assert(hana::Functor<S>::value,
  37         "hana::transform(xs, f) requires 'xs' to be a Functor");
  38     #endif
  39
  40         return Transform::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
  41     }
  42     //! @endcond
  43
  44     template <typename Fun, bool condition>
  45     struct transform_impl<Fun, when<condition>> : default_ {
  46         template <typename Xs, typename F>
  47         static constexpr auto apply(Xs&& xs, F&& f) {
  48             return hana::adjust_if(static_cast<Xs&&>(xs),
  49                                    hana::always(hana::true_c),
  50                                    static_cast<F&&>(f));
  51         }
  52     };
  53
  54     template <typename S>
  55     struct transform_impl<S, when<Sequence<S>::value>> {
  56         //! @cond
  57         template <typename F>
  58         struct transformer {
  59             F f;
  60             template <typename ...Xs>
  61             constexpr auto operator()(Xs&& ...xs) const {
  62                 return hana::make<S>((*f)(static_cast<Xs&&>(xs))...);
  63             }
  64         };
  65         //! @endcond
  66
  67         template <typename Xs, typename F>
  68         static constexpr auto apply(Xs&& xs, F&& f) {
  69             // We use a pointer to workaround a Clang 3.5 ICE
  70             return hana::unpack(static_cast<Xs&&>(xs),
  71                                 transformer<decltype(&f)>{&f});
  72         }
  73     };
  74 BOOST_HANA_NAMESPACE_END
  75
  76 #endif // !BOOST_HANA_TRANSFORM_HPP